Sierra Blaster, Black Cat, and Tannerite manufacturers and customers (target shooters) might disagree.
From the ATF:
"Persons who manufacture explosives for their personal, non-business use (e.g., making fireworks to set off on your own property or mixing binary explosive components to remove a stump in your own yard) are not required to have a manufacturer’s license." (and you only need a manufacturers license for usage/ignition if it's for business use)
I'm not manufacturing anything, it's .22 blanks from the hardware store, only difference is they are being triggered in a barrel made of granite and not steel. I can't speak for other states but they are allowed here.
Small arms ammunition is exempt [18 U.S.C. 845(a)(4), 27 CFR 555..11 : definition of “ammunition”, 555.141(a)(4)] from explosives terminology/regulation.
This is why, I presume at least, you don't need a license to make exploding tannerite targets, or a license to actually use mini blaster-type equipment, only training topurchase the loads. There is no permit/license offered for this on the ATF site even if you wanted to get one.
If you have seen something saying otherwise I'd be interested to see it.